Ball grid array (BGA) packages are widely used in the art because they have high I/O densities and can be directly arranged on the printed circuit board according to a surface mount technology (SMT). As known, the BGA package should be tested according to a testing procedure. Since the BGA package has a higher I/O density and unique ball contacts, the method for testing the BGA package is more complicated than that for testing the conventional semiconductor package. Generally, the ball contacts of the BGA package are conductively connected to the contact pads of the printed circuit board via a BGA test socket assembly. In this instance, the ball contacts of the BGA package need not to be soldered onto the contact pads of the printed circuit board.
Referring to FIG. 1(a), a cross-sectional view of a conventional BGA test socket assembly is illustrated. The BGA test socket assembly is employed for interconnecting the ball contacts of the BGA package and the conducting holes of the printed circuit board. The BGA test socket assembly 1 of FIG. 1(a) comprises a socket body 10 and a clip member 11. The socket body 10 comprises an interface layer 101 and a receptacle 102. There are perforations 103 extending through the interface layer 101 between upper and lower surfaces thereof so as to accommodate corresponding number of resilient contact members 104. A ball grid array package 12 is accommodated in the receptacle 102 and clamped by the clip member 11 such that the ball contacts 120 are in contact with the upper terminal ends 104a of corresponding resilient contact members 104. The lower terminal ends 104b (i.e. pins) of the resilient contact members 104 project downwardly from the socket body 10 to touch corresponding conductive holes 130 of the printed circuit board 13. By means of the BGA test socket assembly 1, the performance properties of the ball grid array package 12 would be tested accordingly.
Please refer to FIG. 1(b). The BGA test socket assembly 1 of FIG. 1(a) is mounted on the printed circuit board 13 by inserting the lower terminal ends 104b of the resilient contact members 104 into the conductive holes 130. Since the lower terminal ends 104b of the resilient contact members 104 should be precisely inserted into the corresponding conductive holes 130 to perform the test procedure, the printed circuit board 13 should be tailored and not cost-effective. That is to say, the printed circuit board 13 is only applied to the unreal system. In addition, due to the high density of the resilient contact members 104, the lower terminal ends 104b are readily broken during the period of inserting them into the conductive holes 130 and thus erroneous test results may often occur. Moreover, with increasing improvement, the semiconductor packages are developed toward minimization and high integration, and thus the pin density of the semiconductor packages are growing higher and higher. In other words, the pitch between two adjacent pins becomes shorter and shorter as well as the pitch between the terminal pads on the test printed circuit board. The possibility of generating erroneous test results is increased.
Another BGA test socket assembly was disclosed in U.S. Pat. No. 5,702,255, entitled “BALL GRID ARRY SOCKET ASSEMBLY”, which was filed on Dec. 30, 1997, and the contents of which are hereby incorporated by reference. The BGA test socket assembly 2 of FIG. 2 comprises a socket body 20 and a clip member 21. The socket body 20 comprises an interface layer 201 and a receptacle 202. There are perforations 203 extending through the interface layer 201 between upper and lower surfaces thereof so as to accommodate corresponding number of resilient contact members 204. A ball grid array package 22 is accommodated in the receptacle 202 and clamped by the clip member 21 such that the ball contacts 220 are in contact with the upper terminal ends 204a of corresponding resilient contact members 204. The lower terminal ends 204b (i.e. ball pins) of the respective resilient contact members 204 project downwardly from the socket body 20 to touch corresponding contact pads 230 on the printed circuit board 23 of an unreal system. By means of the BGA test socket assembly 2, the performance properties of the ball grid array package 22 would be tested accordingly.
As known, the process for forming the ball pins 204b on the lower terminal ends of the resilient contact members 204 is complicated. In addition, the process for assembling the resilient contact members 204 in the BGA test socket assembly 2 is time-consuming. Accordingly, a problem of poor connection may occur. If several BGA test socket assemblies 2 are intended to mount on the printed circuit board 23, each BGA test socket assembly 2 should be precisely aligned with the corresponding contact portions of the printed circuit board 23, and thus the testing procedure is not effective for testing plural BGA test socket assemblies 2 when a single printed circuit board 23 is used.
With increasing development of semiconductor industries, the size and shape of semiconductor package will be varied according to the manufacturer's design and/or the market's requirement. For complying with the semiconductor package to be tested, the size and the shape of the retaining base used in the test socket assembly should be varied accordingly. In the conventional test socket assembly, however, the retaining base is not replaceable and has unchanged size and shape. Under this circumstance, in order to test the semiconductor packages conforming to different specifications, different moulds should be fabricated to produce proper test socket assemblies. Therefore, the testing process is not cost effective and is time-consuming.
Accordingly, the above-described prior art method is not a perfect design and has still many disadvantages to be solved. In views of the above-described disadvantages resulted from the prior art, the applicant keeps on carving unflaggingly to develop a method and socket assembly for testing a ball grid array package according to the present invention through wholehearted experience and research.